feat(coding-agent): add hidden thinking label api closes #2673

packages/coding-agent/CHANGELOG.md

@@ -14,6 +14,7 @@
 
 - Added `ToolDefinition.prepareArguments` hook to prepare raw tool call arguments before schema validation, enabling compatibility shims for resumed sessions with outdated tool schemas
 - Built-in `edit` tool now uses `prepareArguments` to silently fold legacy top-level `oldText`/`newText` into `edits[]` when resuming old sessions
+- Added `ctx.ui.setHiddenThinkingLabel()` so extensions can customize the collapsed thinking label in interactive mode, with a no-op in RPC mode and a runnable example extension in `examples/extensions/hidden-thinking-label.ts` ([#2673](https://github.com/badlogic/pi-mono/issues/2673))
 
 ### Fixed
 

packages/coding-agent/examples/extensions/README.md

@@ -52,6 +52,7 @@ cp permission-gate.ts ~/.pi/agent/extensions/
 | `qna.ts` | Extracts questions from last response into editor via `ctx.ui.setEditorText()` |
 | `status-line.ts` | Shows turn progress in footer via `ctx.ui.setStatus()` with themed colors |
 | `widget-placement.ts` | Shows widgets above and below the editor via `ctx.ui.setWidget()` placement |
+| `hidden-thinking-label.ts` | Customizes the collapsed thinking label via `ctx.ui.setHiddenThinkingLabel()` |
 | `model-status.ts` | Shows model changes in status bar via `model_select` hook |
 | `snake.ts` | Snake game with custom UI, keyboard handling, and session persistence |
 | `send-user-message.ts` | Demonstrates `pi.sendUserMessage()` for sending user messages from extensions |

packages/coding-agent/examples/extensions/hidden-thinking-label.ts

@@ -0,0 +1,57 @@
+/**
+ * Hidden Thinking Label Extension
+ *
+ * Demonstrates `ctx.ui.setHiddenThinkingLabel()` for customizing the label shown
+ * when thinking blocks are hidden.
+ *
+ * Usage:
+ *   pi --extension examples/extensions/hidden-thinking-label.ts
+ *
+ * Test:
+ *   1. Load this extension
+ *   2. Hide thinking blocks with Ctrl+T
+ *   3. Ask for something that produces reasoning output
+ *   4. The collapsed thinking block label will show the custom text
+ *
+ * Commands:
+ *   /thinking-label <text>   Set a custom hidden thinking label
+ *   /thinking-label          Reset to the default label
+ */
+
+import type { ExtensionAPI, ExtensionContext } from "@mariozechner/pi-coding-agent";
+
+const DEFAULT_LABEL = "Pondering...";
+
+export default function (pi: ExtensionAPI) {
+	let label = DEFAULT_LABEL;
+
+	const applyLabel = (ctx: ExtensionContext) => {
+		ctx.ui.setHiddenThinkingLabel(label);
+	};
+
+	pi.on("session_start", async (_event, ctx) => {
+		applyLabel(ctx);
+	});
+
+	pi.on("session_switch", async (_event, ctx) => {
+		applyLabel(ctx);
+	});
+
+	pi.registerCommand("thinking-label", {
+		description: "Set the hidden thinking label. Use without args to reset.",
+		handler: async (args, ctx) => {
+			const nextLabel = args.trim();
+
+			if (!nextLabel) {
+				label = DEFAULT_LABEL;
+				ctx.ui.setHiddenThinkingLabel();
+				ctx.ui.notify(`Hidden thinking label reset to: ${DEFAULT_LABEL}`);
+				return;
+			}
+
+			label = nextLabel;
+			ctx.ui.setHiddenThinkingLabel(label);
+			ctx.ui.notify(`Hidden thinking label set to: ${label}`);
+		},
+	});
+}

packages/coding-agent/src/core/extensions/runner.ts

@@ -178,6 +178,7 @@ const noOpUIContext: ExtensionUIContext = {
 	onTerminalInput: () => () => {},
 	setStatus: () => {},
 	setWorkingMessage: () => {},
+	setHiddenThinkingLabel: () => {},
 	setWidget: () => {},
 	setFooter: () => {},
 	setHeader: () => {},

packages/coding-agent/src/core/extensions/types.ts

@@ -127,6 +127,9 @@ export interface ExtensionUIContext {
 	/** Set the working/loading message shown during streaming. Call with no argument to restore default. */
 	setWorkingMessage(message?: string): void;
 
+	/** Set the label shown for hidden thinking blocks. Call with no argument to restore default. */
+	setHiddenThinkingLabel(label?: string): void;
+
 	/** Set a widget to display above or below the editor. Accepts string array or component factory. */
 	setWidget(key: string, content: string[] | undefined, options?: ExtensionWidgetOptions): void;
 	setWidget(

packages/coding-agent/src/modes/interactive/components/assistant-message.ts

@@ -9,17 +9,20 @@ export class AssistantMessageComponent extends Container {
 	private contentContainer: Container;
 	private hideThinkingBlock: boolean;
 	private markdownTheme: MarkdownTheme;
+	private hiddenThinkingLabel: string;
 	private lastMessage?: AssistantMessage;
 
 	constructor(
 		message?: AssistantMessage,
 		hideThinkingBlock = false,
 		markdownTheme: MarkdownTheme = getMarkdownTheme(),
+		hiddenThinkingLabel = "Thinking...",
 	) {
 		super();
 
 		this.hideThinkingBlock = hideThinkingBlock;
 		this.markdownTheme = markdownTheme;
+		this.hiddenThinkingLabel = hiddenThinkingLabel;
 
 		// Container for text/thinking content
 		this.contentContainer = new Container();
@@ -39,6 +42,16 @@ export class AssistantMessageComponent extends Container {
 
 	setHideThinkingBlock(hide: boolean): void {
 		this.hideThinkingBlock = hide;
+		if (this.lastMessage) {
+			this.updateContent(this.lastMessage);
+		}
+	}
+
+	setHiddenThinkingLabel(label: string): void {
+		this.hiddenThinkingLabel = label;
+		if (this.lastMessage) {
+			this.updateContent(this.lastMessage);
+		}
 	}
 
 	updateContent(message: AssistantMessage): void {
@@ -70,8 +83,10 @@ export class AssistantMessageComponent extends Container {
 					.some((c) => (c.type === "text" && c.text.trim()) || (c.type === "thinking" && c.thinking.trim()));
 
 				if (this.hideThinkingBlock) {
-					// Show static "Thinking..." label when hidden
+					// Show static thinking label when hidden
-					this.contentContainer.addChild(new Text(theme.italic(theme.fg("thinkingText", "Thinking...")), 1, 0));
+					this.contentContainer.addChild(
+						new Text(theme.italic(theme.fg("thinkingText", this.hiddenThinkingLabel)), 1, 0),
+					);
 					if (hasVisibleContentAfter) {
 						this.contentContainer.addChild(new Spacer(1));
 					}

packages/coding-agent/src/modes/interactive/interactive-mode.ts

@@ -164,6 +164,8 @@ export class InteractiveMode {
 	private loadingAnimation: Loader | undefined = undefined;
 	private pendingWorkingMessage: string | undefined = undefined;
 	private readonly defaultWorkingMessage = "Working...";
+	private readonly defaultHiddenThinkingLabel = "Thinking...";
+	private hiddenThinkingLabel = this.defaultHiddenThinkingLabel;
 
 	private lastSigintTime = 0;
 	private lastEscapeTime = 0;
@@ -1325,6 +1327,19 @@ export class InteractiveMode {
 		this.ui.requestRender();
 	}
 
+	private setHiddenThinkingLabel(label?: string): void {
+		this.hiddenThinkingLabel = label ?? this.defaultHiddenThinkingLabel;
+		for (const child of this.chatContainer.children) {
+			if (child instanceof AssistantMessageComponent) {
+				child.setHiddenThinkingLabel(this.hiddenThinkingLabel);
+			}
+		}
+		if (this.streamingComponent) {
+			this.streamingComponent.setHiddenThinkingLabel(this.hiddenThinkingLabel);
+		}
+		this.ui.requestRender();
+	}
+
 	/**
 	 * Set an extension widget (string array or custom component).
 	 */
@@ -1405,6 +1420,7 @@ export class InteractiveMode {
 		if (this.loadingAnimation) {
 			this.loadingAnimation.setMessage(`${this.defaultWorkingMessage} (${keyText("app.interrupt")} to interrupt)`);
 		}
+		this.setHiddenThinkingLabel();
 	}
 
 	// Maximum total widget lines to prevent viewport overflow
@@ -1557,6 +1573,7 @@ export class InteractiveMode {
 					this.pendingWorkingMessage = message;
 				}
 			},
+			setHiddenThinkingLabel: (label) => this.setHiddenThinkingLabel(label),
 			setWidget: (key, content, options) => this.setExtensionWidget(key, content, options),
 			setFooter: (factory) => this.setExtensionFooter(factory),
 			setHeader: (factory) => this.setExtensionHeader(factory),
@@ -2262,6 +2279,7 @@ export class InteractiveMode {
 						undefined,
 						this.hideThinkingBlock,
 						this.getMarkdownThemeWithSettings(),
+						this.hiddenThinkingLabel,
 					);
 					this.streamingMessage = event.message;
 					this.chatContainer.addChild(this.streamingComponent);
@@ -2617,6 +2635,7 @@ export class InteractiveMode {
 					message,
 					this.hideThinkingBlock,
 					this.getMarkdownThemeWithSettings(),
+					this.hiddenThinkingLabel,
 				);
 				this.chatContainer.addChild(assistantComponent);
 				break;

packages/coding-agent/src/modes/rpc/rpc-mode.ts

@@ -167,6 +167,10 @@ export async function runRpcMode(session: AgentSession): Promise<never> {
 			// Working message not supported in RPC mode - requires TUI loader access
 		},
 
+		setHiddenThinkingLabel(_label?: string): void {
+			// Hidden thinking label not supported in RPC mode - requires TUI message rendering access
+		},
+
 		setWidget(key: string, content: unknown, options?: ExtensionWidgetOptions): void {
 			// Only support string arrays in RPC mode - factory functions are ignored
 			if (content === undefined || Array.isArray(content)) {